1. Copyright Notice
This patent document contains information subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent, as it appears in the U.S. Patent and Trademark Office files or records but otherwise reserves all copyright rights whatsoever.
2. Field of the Invention
The present invention, in certain respects, may relate to hard disks. In other respects, the present invention may relate to a hard disk""s read/write heads and to hindering pole tip protrusion (PTP).
3. Description of Background Information
Hard disks are being manufactured with increased access speeds and storage capacities. Manufacturers of these (present day and future) improved-performance hard disks have decreased the distance between the hard disk""s read/write heads and its disk media. As a result, slight variations in the positioning or dimensions of the heads or of the disk media can cause the heads and the disk media to collide. For example, such a collision can be caused by protrusion of the pole tips of the write portion of a given read/write head, a phenomenon referred to as pole tip protrusion (PTP).
PTP can be caused by high frequency writing, which causes the thermal expansion of the pole tips. Such thermal expansion is caused by eddy current heating and coil heating. PTP can cause problems such as off-track writing (due to frictional forces) and high servo PES (due to the dragging of the head by the pole tip). PTP can result in drive failure.
The present invention is provided to hinder the occurrence of PTP in the write elements of hard disk read/write heads.
In accordance with one aspect of the invention, a hard disk is provided with tools for limiting the duty cycle (a group of variations of load with time). The write current is controlled by, e.g., limiting the duration of a given write cycle. The write cycle may involve writing data continuously along adjacent portions of the disk media (e.g., writing of data in adjacent segments of a track in the outer diameter (OD) region of a platter), with an intermittent duty write current. The invention may also be directed to any portion of such a hard disk or to any set or subset of acts performed by the hard disk. The invention may also be directed to computer readable media encoded to perform any acts disclosed herein.
In one embodiment, the write cycle is limited to a thermal time constant of approximately 0.5 to 1.0 msec. In another embodiment the write cycle is limited to a longer period, e.g., 2-100 msec.